LPT: If you're on the verge of an impulse buy, set the item down and walk around the store for 10 minutes.

I used to struggle with impulse buys. I found that it's a lot easier to say "maybe in 10 minutes" than to outright say "no" when the item is in my hands. I just put it back on the shelf and walk around a bit - no pressure, no battle of willpower. I've found that after 10 minutes away from the item, the pull to buy it is usually much lower, and if I still want the thing, it usually ends up being a good purchase that I won't regret.

Obviously, the key thing here is to separate yourself from the item - both during the 10 minutes and when you make your decision. Don't go back to it when it's decision time.